Rove beetles are a huge family of beetles. They typically don’t look much like beetles, since their hardened forewings (elytra) are so short you can see the abdominal segments at the hind part of the body. Despite the short elytra, most species have fully functional, membranous wings folded under the wing covers, so most are capable of flight. The antennae are threadlike, sometimes clubbed.
The hardened forewings of rove beetles are typically short or reduced (brachypterous). Together, these elytra (that are shell-like in most other beetles) are usually about the same size as the pronotum (the thorax plate, between the elytra and the head); from above, you can usually see 5–6 of the abdominal segments at the rear of the body. In some species, only 3 or 4 of the segments are visible; in a few, none.
Rove beetles are typically active, fast-moving insects. In flight, they may seem wasplike. Walking around, they often flip up or wiggle their flexible, exposed abdomen, especially when frightened. The bodies of most rove beetles are elongated and almost snakelike, but some species are oval.
With about 540 genera in 26 subfamilies in North America north of Mexico, this is a staggeringly large group of insects. This page is just an introduction. For pictures of many of the species, see the rove beetles pages on BugGuide, sponsored by Iowa State University. Even then, you will probably not be able to identify particular species. To identify rove beetles to species, entomologists usually must dissect the genitalia of preserved specimens.
When rove beetles curl their abdomen tips upward, it can seem like they’re about to sting — but they are not capable of stinging. Still, you should handle them with care, since they can nip you with their jaws.
Also, some species can emit repellant chemicals. The worst of these are mostly associated with rove beetles that don’t occur in North America, but a few do occur on our continent. In general, these rove beetles (notably in genus Paederus) are boldly marked with reddish-orange and black warning colors. Don’t slap them, as the toxic chemical (pederin) is in the insect’s hemolymph (“blood”).
Similar species: Rove beetles are often confused with earwigs (order Dermaptera), which are also narrow, flexible, flattened insects with exposed abdominal segments. Earwigs, however, have a pair of pincers at the hind end, while rove beetles have a few appendages at the tip of the abdomen that are not opposable or forceps-like.
There is a great deal of variation in the rove beetle family, and some oddball groups of rove beetles do not match the above description much at all.
Adult length: most species are less than ½ inch long, but some can reach 1 inch in length. The abdomen can telescope somewhat, making exact measurements difficult in live specimens.
Statewide. Different species may have varying habitat preferences, thus different distribution patterns within the state.
Habitat and Conservation
Most rove beetles are limited to moist habitats. The majority live in protected places on the ground: under logs, rocks, amid leaf litter, and so on.
While most other beetles have a large pair of hardened forewings protecting the hind portion of the body, rove beetles’ shortened forewings renders them more susceptible to drying out. This helps explain their association with cool, damp places under logs and such. Meanwhile, their flexible abdomen allows them to slip easily into tight crevices.
Rove beetles can be attracted to lights at night.
Foods account for particular habitat preferences. Some rove beetles are variously associated with carrion, dung, fungi, rotting fallen fruits, washed-up kelp on seashores, and so on.
Several rove beetles specialize in habitats near water, such as the banks of streams, ponds, or lakes, or on seashores.
Some rove beetles are adapted to life in caves or in soil, and some of these species lack functioning eyes.
Specifics of existential threats, population trends, and management considerations are largely unknown for many species of rove beetles.
Some types of rove beetles are closely linked to other species. This can be the situation with rove beetles that are highly specialized to live alongside ants or termites in their colonies. Their fortunes are tied to the destiny of the specific types of ants or termites whose nests they inhabit.
In other cases, population declines may be linked to habitat loss and fragmentation. For example, some species may require old-growth hardwood or mixed hardwood forests that have plenty of standing mature trees and rotting logs lying on the ground. As those habitats disappear, the rove beetles disappear, too.
Rove beetles are probably not personally appealing to most people. Fortunately for them, the declines of other, prettier or more charismatic species can prompt people to protect the habitats they all rely on.
Food
In such a large family, there is great diversity in diet. Many species are carnivorous, preying on insects and other small invertebrates such as soil-dwelling nematodes, mites, or springtails. Others are scavengers, eating decaying plant matter, or rotting fruits, dead insects or other animals, fungi, and so on. Some are attracted to dead or decaying matter in order to prey on other insects that scavenge from such materials.
Some species are generalists, eating a wide variety of foods, while others are more specialized for eating only certain types of foods.
Status
Some rove beetles have been listed as Missouri species of conservation concern:
- Aleochara speculicollis
- Bibloplectus chickasaw
- Deinopsis virginiana
- Derops divalis
- Gennadota canadensis
- Hesperus stehri
- Lordithon niger
- Oxybleptes kiteleyi
- Sepedophilus campbelli
- Xylodromus capito
In Missouri, most of the above are designated “unrankable” due to a lack of information or due to substantially conflicting information about status or trends. Globally, all of the above bear the parallel rank of “unranked,” meaning that their status has not yet been assessed.
Among all the animal families in North America north of Mexico, the rove beetle family (Staphylinidae) is the largest, with about 4,400 species described officially by scientists, plus many that remain undescribed. Well more than 5,000 are probable.
The rove beetles may be the largest family globally, too, with around 56,000 species in 3,500 genera. It is possible the ichneumon wasp family (Ichneumonidae) might be larger, as some estimate that family to include about 60,000 species globally.
Many rove beetle species remain undescribed by science, especially in tropical regions, where scientists estimate that some 75 percent of species have not yet been formally described. Entomologists are hoping to catalogue as many of these as possible before they go extinct.
Life Cycle
Like other beetles, the progression is from egg to grublike larva; then, after a series of larval molts, the insect becomes a pupa (an inactive stage much like a butterfly’s chrysalis), then emerges as a sexually mature, winged adult. The larval stage of rove beetles is often flattened, and the time between hatched egg and the start of pupation can be only days or a few weeks. As adults, they can live a relatively long time.
Human Connections
Rove beetles can definitely be beneficial for human interests, since many species prey on insect pests. They can suppress pests of crops, gardens, and forests; they can suppress numbers of mosquitoes and fleas.
In some tropical regions, certain rove beetles prey on mosquito larvae and pupae that develop in water that collects in the floral bracts of flowers (Heliconia, the “lobster-claw” or “false bird-of-paradise” plants), and in hollow bamboo stalks. Their predation no doubt helps reduce mosquitoes in those regions, where mosquito-borne diseases threaten human health.
In central Asia, rove beetles have been credited for helping human health by preying on the fleas that carry sylvatic plague.
Since rove beetles are part of the insect community associated with decaying corpses, forensic scientists can use their presence, stage of development, and numbers at a crime scene to gauge the time of death and help solve criminal cases.
Certain rove beetles (such as those in genus Paederus) have a toxic chemical in their body fluids that, if it gets on human skin, can cause a burning, blistering rash. Lucky for us, these insects are more common overseas than they are in North America. Interestingly, the Chinese have been using extracts of this chemical (pederin) to treat a variety of maladies for more than a thousand years. Today, researchers are studying pederin and related chemicals for possible use in anticancer drugs.
The beetles, order Coleoptera, are unquestionably the most diverse group of organisms on Earth. One out of every four animal species on our planet is some kind of beetle. This amazing diversity inspired a famous quote about beetles, usually attributed to the English scientist J.B.S. Haldane. Supposedly, when asked what he could surmise about the mind of God — based on what was known by science — he commented that the Creator must have “an inordinate fondness for beetles.” By extension, the rove beetles, being one of the largest groups within the largest group, must be extra-special favorites!
The family name, Staphylinidae, is pronounced “STAFF-uh-LIN-uh-dee.” The word ultimately comes from the Greek staphylē, meaning “a bunch of grapes.” As an insect name, “staphylin” under various spellings might date back to before 300 BC. It’s not clear which of the many European beetles first received the name, but some people have suggested it might have been a group that have black, round bodies and secrete bright red fluids — thus resembling grapes. These suggested namesakes, commonly called bloody-nosed beetles (genus Timarcha), are actually leaf beetles (chrysomelids), not rove beetles.
Ecosystem Connections
As predators of insects and other small animals, rove beetles serve to keep populations of their prey species in check. The ones that are scavengers chew on dead, rotting vegetation or animal matter; in this case, rove beetles help the decomposition process, enriching the soil and removing detritus, rot, and foul materials from the landscape. In some cases, it can be difficult to tell if a rove beetle that is present on dung or decaying material is eating the material directly, or if it is preying on the various grubs, maggots, and such that are.
Many kinds of animals prey on rove beetles, including spiders, assassin bugs, robber flies, salamanders, toads, frogs, lizards, snakes, birds, and even bats (remember that most rove beetles can fly).
Some types of rove beetles are known to pollinate certain types of flowers. One species, for example, eats the pollen of skunk cabbages and, in the process, pollinates the flowers.
Some types of rove beetles feed on certain types of mushrooms or other fungi. Meanwhile, certain types of fungi can infect, digest, and kill rove beetles. Some of these fungi specialize in certain groups of rove beetles.
Some rove beetles are specialized to live alongside other animals in their nests. Some live in the nest colonies of ants, termites, and bees. Some of these rove beetles secrete chemicals that pacify the original nest builders. Others live in the nests of rodents, land tortoises, or birds. In many cases, these rove beetles prey on the fleas, mites, fly maggots, and other parasites that pester the nest makers. In some cases, the rove beetles live in the fur of rodents, eating the rodents’ fleas.
Rove beetles have a long history on Earth, with a fossil record that goes back more than 200 million years ago to the Upper Triassic period.
